[Feature] Support exact percentile aggregate function (#6410)

Support to calculate the exact percentile value array of numeric column `col` at the given percentage(s).

docs/en/sql-reference/sql-functions/aggregate-functions/percentile.md

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+---
+{
+    "title": "PERCENTILE",
+    "language": "en"
+}
+---
+
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+
+# PERCENTILE
+## Description
+### Syntax
+
+`PERCENTILE(expr, DOUBLE p)`
+
+Calculate the exact percentile, suitable for small data volumes. Sort the specified column in descending order first, and then take the exact p-th percentile. The value of p is between 0 and 1
+
+Parameter Description:
+expr: required. The value is an integer (bigint at most).
+p: The exact percentile is required. The value is [0.0,1.0]
+
+## example
+```
+MySQL > select `table`, percentile(cost_time,0.99) from log_statis group by `table`;
++---------------------+---------------------------+
+| table    |         percentile(`cost_time`, 0.99)|
++----------+--------------------------------------+
+| test     |                                54.22 |
++----------+--------------------------------------+
+
+## keyword
+PERCENTILE